Hose can best be described as a flexible pipe. Its purpose is to contain and transmit fluid from one location to another safely. Fluids include liquid, gas, solids in a fluidic state and combinations of these catagories. Hose has advantages over pipe inasmuch as it is flexible, it absorbs vibration, it may handle corrosive fluids, it comes in a great variety of sizes, it is sound dampening, and it is easily stored.
Hose is constructed of three basic elements, (1) the tube or inner liner which is the element which contains, conveys, and resists the fluid inside. It transmits the forces created by internal pressure of the fluid to the strength member of the hose; (2) the reinforcement or strength member of the hose, commonly referred to as "hose reinforcement", reacts to and resists the forces of the fluid pressure, commonly called "hoop strength"; and (3) the cover which protects the hose reinforcement from physical damage and resists the external environment.
Materials used to construct the tube or inner liner and the cover consists of, in the most common cases, rubber or plastic, while the hose reinforcement usually comprises yarns, fabrics, and metals in the form of filaments, wires, fabric, braid, sprials, etc. Rubber is used in its broad sense including all elastomeric materials--natural, synthetic, and compounds and structures thereof, while plastics include the wide spectrum of thermoplastic materials. The hose reinforcement includes materials made from cotton, synthetics, or combinations thereof, and metals including steel, copper, aluminum, and platings thereon such as zinc, brass, cadmium, and tin.
Available today are a wide range of basic elastomers to choose from, and many types can be blended together in almost unlimited combinations to obtain different properties. Common rubbers available are neoprene, natural rubber, polyisoprene butyl, nitrile, SBR, hypalon, ethylene, propylene, chloronated polyethylene (CPE), fluorocarbons, epichlorohydrin, and epichlorohydrin/ethylene oxide. Examples of thermoplastic materials include polyvinyl chloride (PVC), polyethylene (PE), nylon, polyester, polyurethane (TPU), and EVA. In addition, fibers commonly used in hose construction comprise cotton, rayon, glass, nylon, polyester, asbestos, fiber B, and nomex nylon.
The five basic types of hose reinforcements are identified by the method of manufacture or application over the inner tube or liner. These five types are braid, spiral, wrapped ply, loom, and knit. In braiding, a braid is formed by interweaving cords while they are being applied in a helical spiral over the tube. One-half of the cords are spiraled right-hand, and the other left-hand. The most common hose braiding machines weave cords in a two-over, two-under pattern. When multiple plies are braided, it is important to obtain proper adhesion between plies as well as to the tube and cover. Adhesion is usually obtained by the use of a thin layer of tie gum, often called friction, or by a dough or cement application in and around cores of the braid. Spiral reinforcement is applied in separate plies. The first ply may be laid in a left or right hand spiral and second ply then laid in an opposite spiral. Successive plies are applied in a similar manner, each ply separated by a tie gum layer or dough adhesive. Wrapped ply reinforcement of a woven fabric is often used as hose reinforcement, either as a series of multiple plies, or in conjunction with a spiral wire. The fabric is prepared by a calendering or coating the fabric with rubber compound, i.e., tie gum, which enables the fabric to adhere to adjacent plies, to the tube, and to the cover. In addition, the tie gum may first be applied to the tube and then wrapped with the woven fabric. Loom reinforcement of hose is made with cords wound at a closed circular pitch while longitudinal (wrap) yarns are interwoven with the circular wound cords. Knit reinforcement of both is accomplished by applying reinforcing yarns over the tube in a circular knitting machine. Variations of the knit pattern include a plain knit, lock-stitch, or wrap knit.
For more extensive information, the reader is referred to the publication HOSE HAND BOOK, RUBBER MANUFACTURERS ASSOCIATION, 1901 Pennsylvania Avenue, Washington N.W., D.C. 20026 (1979).
The inner tube or liner must be firm enough in the unvulcanized state to resist deformation and stretch under normal processing conditions described above. When the tube is too thin or too soft to withstand subsequent processing, or when the internal diameter must be kept within a narrow range, it is supported on a mandrel. The mandrel is usually as long as the hose to be made and has a round or other cross-section as desired.
In many cases, hoses utilized for pressurized liquids are wrapped with hose reinforcement applied under tension and the material chosen for the inner tube is not sufficiently firm to resist deformation and stretch and therefore must be vulcanized prior to application of the tie gum and hose reinforcement. In addition, many times the inner tube must be supported on an internal mandrel during this method of processing. The present state of the art in constructing hose for pressurized liquids is to employ a mandrel at least as long as the hose to be made, the mandrel being removed either before or after vulcanization of the tie gum and hose cover. If the mandrel is removed prior to the final vulcanization, the interior of the hose is supported during vulcanization by fluid under pressure.
Because of the problems that are inherent in removing the mandrel from a completed hose (before or after final vulcanization), hose length has been limited in construction to lengths which can be physically handled during processing and where the mandrel can be removed without substantial danger of harming the hose.
Hose made by the processes above described perform the function of resisting forces of fluid pressure which might result in the hose bursting by having a great hoop strength. However, there arises occasions where it is necessary that the hose exhibit high tensile strength, i.e., strength in its longitudinal direction and under some circumstances, extreme resistance to outside abrasion and damage.
Possible application of hose requiring high tensile strength are use of hose in deep undersea mining where the hose serves both to convey minerals recovered from the seabed and to tow a sleigh which gathers the minerals for conveyance to the surface. In addition, the unsupported stretching of hose for long distances such as between ships at sea during refueling requires that the hose utilized exhibit high tensile strength, both for its own weight and the weight of the fuel interior to the hose, and to prevent the hose from separating if the two ships pull apart. Hoses exhibiting high tensile strength for such refueling application perform a dual function, that of keeping the ships together, and preventing the breaking of the hose line and aborting a successful transfer of fuel.
Further, high tensile strength hose is useful for ship to shore liquid unloading where, in addition to the high tensile strength necessary, the hose cover must be highly resistant to abrasion caused by coral reefs, sand, surf, and the like. The longitudinal load imposed on the hose would be due to wave motion, currents, wind, tide, possible drifting of the ship, and the like.
In addition, there are situations where the qualities of high tensile strength in the longitudinal direction and high resistance to abrasion and damage are necessary such as if the hose were employed as a float-sink hose, i.e., the hose is designed to float while empty and then sink when filled with fluid, such as might be used in an installation between ship and shore, the hose being subjected to possible damage if struck by foreign objects, such as a passing ship. In such a case, if the hose could closely approach characteristics of an armour plated hose and still remain flexible, it is obvious that there would be much use.
In addition, it would be useful if the high tensile strength member of the hose were such that it could readily be separated from the hose for situations where it is no longer needed, or due to bulkiness in transportation or in storage, the inner hose and the outer covering could be shipped and stored separately. An example of use of the above separable hose and hose covering would be in temporary suspending of hose between two points until permanent support is provided at which time the outer supporting cover of the hose is removed and the hose theretofore within the covering be supported by the later constructed supporting member.
Further, by the combination of an inner hose and an outer, removable hose covering, ultra light inner hoses may be utilized, possibly even without hose reinforcement in the inner hose, by placing the hose reinforcement in the high tensile strength removable hose covering.
It is to these ends that the subject invention is directed, i.e., to present an invention and method of construction of a hose which exhibits high tensile strength as well as abrasion or damage resistance and is separable into two components, an inner hose for conveying the fluid and an outer removable, reusable high tensile strength hose covering.